The present invention relates to a device adapted to detect the presence of a resonant circuit of a passive or active transponder in its proximity, without requiring contact between the device and the resonant circuit.
Devices for reading or writing passive or active transponders require a significant amount of energy for their operation. If these devices are applied in battery-operated units, the consumption of the entire unit must be as low as possible so as to ensure the longest possible operating endurance. Devices for reading or writing active or passive transponders are usually applied to battery-operated units by means of auxiliary electronic activation circuits, capable of activating communication with the transponder when a transponder is believed to be present, in order to minimize consumption. Examples of embodiments in this regard are units that are activated by means of buttons or by means of detectors for sensing the presence of the hand or of the person, of the infrared or other type, such as to activate the unit only if a person is located very close to the reading and writing device of said unit. The main drawbacks of such embodiments consist in that the unit is activated even in the absence of the transponder, i.e., of the resonant circuit, and they are also costly, since they require additional components that are independent of the read-write circuit.